(function () {
    var BASE64_MAPPING = [
      'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
      'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
      'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
      'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
      'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
      'o', 'p', 'q', 'r', 's', 't', 'u', 'v',
      'w', 'x', 'y', 'z', '0', '1', '2', '3',
      '4', '5', '6', '7', '8', '9', '+', '/'
    ];
  
    /** 
     *ascii convert to binary 
     */
    var _toBinary = function (ascii) {
      var binary = new Array();
      while (ascii > 0) {
        var b = ascii % 2;
        ascii = Math.floor(ascii / 2);
        binary.push(b);
      }
      /* 
      var len = binary.length; 
      if(6-len > 0){ 
          for(var i = 6-len ; i > 0 ; --i){ 
              binary.push(0); 
          } 
      }*/
      binary.reverse();
      return binary;
    };
  
    /** 
     *binary convert to decimal 
     */
    var _toDecimal = function (binary) {
      var dec = 0;
      var p = 0;
      for (var i = binary.length - 1; i >= 0; --i) {
        var b = binary[i];
        if (b == 1) {
          dec += Math.pow(2, p);
        }
        ++p;
      }
      return dec;
    };
  
    /** 
     *unicode convert to utf-8 
     */
    var _toUTF8Binary = function (c, binaryArray) {
      var mustLen = (8 - (c + 1)) + ((c - 1) * 6);
      var fatLen = binaryArray.length;
      var diff = mustLen - fatLen;
      while (--diff >= 0) {
        binaryArray.unshift(0);
      }
      var binary = [];
      var _c = c;
      while (--_c >= 0) {
        binary.push(1);
      }
      binary.push(0);
      var i = 0, len = 8 - (c + 1);
      for (; i < len; ++i) {
        binary.push(binaryArray[i]);
      }
  
      for (var j = 0; j < c - 1; ++j) {
        binary.push(1);
        binary.push(0);
        var sum = 6;
        while (--sum >= 0) {
          binary.push(binaryArray[i++]);
        }
      }
      return binary;
    };
  
    var __BASE64 = {
      /** 
       *BASE64 Encode 
       */
      encoder: function (str) {
        var base64_Index = [];
        var binaryArray = [];
        for (var i = 0, len = str.length; i < len; ++i) {
          var unicode = str.charCodeAt(i);
          var _tmpBinary = _toBinary(unicode);
          if (unicode < 0x80) {
            var _tmpdiff = 8 - _tmpBinary.length;
            while (--_tmpdiff >= 0) {
              _tmpBinary.unshift(0);
            }
            binaryArray = binaryArray.concat(_tmpBinary);
          } else if (unicode >= 0x80 && unicode <= 0x7FF) {
            binaryArray = binaryArray.concat(_toUTF8Binary(2, _tmpBinary));
          } else if (unicode >= 0x800 && unicode <= 0xFFFF) {//UTF-8 3byte  
            binaryArray = binaryArray.concat(_toUTF8Binary(3, _tmpBinary));
          } else if (unicode >= 0x10000 && unicode <= 0x1FFFFF) {//UTF-8 4byte  
            binaryArray = binaryArray.concat(_toUTF8Binary(4, _tmpBinary));
          } else if (unicode >= 0x200000 && unicode <= 0x3FFFFFF) {//UTF-8 5byte  
            binaryArray = binaryArray.concat(_toUTF8Binary(5, _tmpBinary));
          } else if (unicode >= 4000000 && unicode <= 0x7FFFFFFF) {//UTF-8 6byte  
            binaryArray = binaryArray.concat(_toUTF8Binary(6, _tmpBinary));
          }
        }
  
        var extra_Zero_Count = 0;
        for (var i = 0, len = binaryArray.length; i < len; i += 6) {
          var diff = (i + 6) - len;
          if (diff == 2) {
            extra_Zero_Count = 2;
          } else if (diff == 4) {
            extra_Zero_Count = 4;
          }
          //if(extra_Zero_Count > 0){  
          //  len += extra_Zero_Count+1;  
          //}  
          var _tmpExtra_Zero_Count = extra_Zero_Count;
          while (--_tmpExtra_Zero_Count >= 0) {
            binaryArray.push(0);
          }
          base64_Index.push(_toDecimal(binaryArray.slice(i, i + 6)));
        }
  
        var base64 = '';
        for (var i = 0, len = base64_Index.length; i < len; ++i) {
          base64 += BASE64_MAPPING[base64_Index[i]];
        }
  
        for (var i = 0, len = extra_Zero_Count / 2; i < len; ++i) {
          base64 += '=';
        }
        return base64;
      },
      /** 
       *BASE64  Decode for UTF-8  
       */
      decoder: function (_base64Str) {
        var _len = _base64Str.length;
        var extra_Zero_Count = 0;
        /** 
         *计算在进行BASE64编码的时候，补了几个0 
         */
        if (_base64Str.charAt(_len - 1) == '=') {
          //alert(_base64Str.charAt(_len-1));  
          //alert(_base64Str.charAt(_len-2));  
          if (_base64Str.charAt(_len - 2) == '=') {//两个等号说明补了4个0  
            extra_Zero_Count = 4;
            _base64Str = _base64Str.substring(0, _len - 2);
          } else {//一个等号说明补了2个0  
            extra_Zero_Count = 2;
            _base64Str = _base64Str.substring(0, _len - 1);
          }
        }
  
        var binaryArray = [];
        for (var i = 0, len = _base64Str.length; i < len; ++i) {
          var c = _base64Str.charAt(i);
          for (var j = 0, size = BASE64_MAPPING.length; j < size; ++j) {
            if (c == BASE64_MAPPING[j]) {
              var _tmp = _toBinary(j);
              /*不足6位的补0*/
              var _tmpLen = _tmp.length;
              if (6 - _tmpLen > 0) {
                for (var k = 6 - _tmpLen; k > 0; --k) {
                  _tmp.unshift(0);
                }
              }
              binaryArray = binaryArray.concat(_tmp);
              break;
            }
          }
        }
  
        if (extra_Zero_Count > 0) {
          binaryArray = binaryArray.slice(0, binaryArray.length - extra_Zero_Count);
        }
  
        var unicode = [];
        var unicodeBinary = [];
        for (var i = 0, len = binaryArray.length; i < len;) {
          if (binaryArray[i] == 0) {
            unicode = unicode.concat(_toDecimal(binaryArray.slice(i, i + 8)));
            i += 8;
          } else {
            var sum = 0;
            while (i < len) {
              if (binaryArray[i] == 1) {
                ++sum;
              } else {
                break;
              }
              ++i;
            }
            unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 1, i + 8 - sum));
            i += 8 - sum;
            while (sum > 1) {
              unicodeBinary = unicodeBinary.concat(binaryArray.slice(i + 2, i + 8));
              i += 8;
              --sum;
            }
            unicode = unicode.concat(_toDecimal(unicodeBinary));
            unicodeBinary = [];
          }
        }
        return unicode;
      }
    };
  
    //window.BASE64 = __BASE64;  
    module.exports = {
      CusBASE64: __BASE64
    }
  })(); 
